The present invention relates generally to a power supply, and more particularly, pertains to a switching regulated power supply for computer equipment and the like.
The following list of patents are believed to be relevant to the subject matter of the present application:
U.S. Pat. No. 3,659,185, "Volt-Second Unbalanced Compensated Two Core Power Transformer", James M. Gregorich, Apr. 25, 1972;
U.S. Pat. No. 3,873,903, "Volt-Second Balancing Means For A High Frequency Switching Power Supply", Philip W. Koetsch et al., Mar. 25, 1975;
U.S. Pat. No. 3,916,286, "Switching Power Supply Common Output Filter", Glenn C. Waehner, Oct. 28, 1975;
U.S. Pat. No. 3,935,526, "DC-To-DC Converter" Yasuiji Kamata et al., Jan. 27, 1976; and
U.S. Pat. No. 4,017,786, "Transformer Saturation Control Circuit For A High Frequency Switching Power Supply", Joseph C. Jensen, Apr. 12, 1977.
In the field of switching regulated power supplies, it has been a general practice to utilize a fairly small capacitor, in the range of a few microfarads, in series with the primary winding of a power transformer. The current pulses through the primary winding are balanced by this capacitor, and a voltage charge develops across the capacitor if there is any unbalance. In practical power supply circuits the optimum size selection of this capacitor must be compromised, resulting in the disadvantage that the capacitor does not prevent saturation of the power transformer but only limits the degree of saturation of the power transformer. Since direct current cannot pass through the capacitor, there is a limit as to the amount of flux that can be developed in one direction in the power transformer. Also, the power transistors of the capacitively balanced switching regulated power supply are subjected to an excessive stress level, and while the power transistors may survive this stress level, the power transistors are subjected to incremental cumulative damage.
Furthermore, the capacitor is an expensive electrical component, physically quite large, and decreases the margins of operation because the capacitor operates by building a voltage across itself. This voltage subtracts from the voltage that is available to drive the power transformer and therefore, all the input voltage is not impressed across the transformer primary windings. The voltage drop across the capacitor can be minimized by increasing the capacitor size, but this increases the stress levels the power transistors must withstand.
Prior art switching regulated power supplies have typically been designed for specific power and load requirements. As a consequence, if a larger power requirement is necessary, it was usually necessary to develop a corresponding power supply meeting that power requirement. The prior art power supplies have not lended themselves to modularized paralleling to satisfy larger power requirements.
The present invention overcomes the shortcomings of the prior art power supplies by providing a switching regulated power supply for modular connection and having charge pump bulk voltage balancing and dynamic flux balancing.